Structural properties of (Mn1-x Fe x )Nb2O6 columbites from X-ray diffraction and IR spectroscopy

Tarantino, S. C. and Zema, M. and Maglia, F. and Domeneghetti, M. C. and Carpenter, M. A. (2005) Structural properties of (Mn1-x Fe x )Nb2O6 columbites from X-ray diffraction and IR spectroscopy. Physics and Chemistry of Minerals, 32. pp. 568-577. ISSN 0342-1791, 1432-2021

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Abstract

A suite of (Mn1-x Fe x )Nb2O6 (x=0, 0.05, 0.25, 0.50, 0.75, 1) columbite samples has been prepared by solid-state reaction from oxides. X-ray diffraction and spectroscopic investigations have been carried out in order to gain different perspectives on how the solid solution adapts at different length scales to cation mixing. X-ray powder diffraction and powder absorption IR spectroscopy data are presented. The powder diffraction data show that there is no significant excess volume of mixing on the Fe–Mn columbite join. All the unit-cell parameters decrease linearly as a function of increasing Fe content. Substitution of Fe2+ for the larger Mn2+ cation causes a decrease in the volume of the A polyhedron, which also becomes more regular with respect to both bond-length and edge-length distortion parameters. No significant variation of the B site has been observed. Wavenumber shifts of the IR peaks nearly all vary linearly with composition, consistent with linear variations of the lattice parameters. Line broadening has been quantified by autocorrelation analysis of the IR spectra. This is interpreted as suggesting that there is some element of local strain or positional disorder at the length scale of second or third nearest neighbours around sites occupied by Fe.

Item Type:	Article
Subjects:	03 - Mineral Sciences
Divisions:	03 - Mineral Sciences
Journal or Publication Title:	Physics and Chemistry of Minerals
Volume:	32
Page Range:	pp. 568-577
Depositing User:	Sarah Humbert
Date Deposited:	21 Oct 2011 17:08
Last Modified:	23 Jul 2013 10:02
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2207

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